This seems likely to be a case where the prefs.js file in the profile is being prevented from updating preferences. That may be due to an antivirus or VPN or other software that may be interfering - or it may be as simple as the prefs.js being read-only. You can investigate this by these steps:

1. click help>troubleshootinginformmaation
2. scroll down to 'profiles' and click 'open folder'
3. you are now in the profile. do you see more than one prefs file, such as prefs-1, prefs-2, etc? That would indicate that thunderbird keeps failing at attempts to update. Check whether prefs.js is read-only. Let me know what you find.

Hi David

Thank you for your prompt response...

In the Directory Entitled - Default Release - Root Directory There are 79 js files but these are all relatively old files, the most recent being 21.5.2024

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In the Directory Entitled - Default Release - Local Directory There are 4 sub folders Cache2 Updated today Contains two folders updated today : Doomed & Entries

                             Doomed is empty - No files  
                             Entries has 5 files - All labelled in Alpha / Numeric Format

Safebrowsing ShortcutCache StartupCache Updated today Contains one LZ4file Updated today

Does any of this help ?

that there are 79 old prefs files indicates there have been problems. check the current prefs.js to see when it was last updated. That may help. And, although I can see the symptoms, I do not have a solution, as there could be many reasons for the file not being updated. You might also test by running help>troubleshootmode to see if you can save settings then

When settings are not retained, it's often caused by 'system' apps like CCleaner that reset settings for apps like TB. Do you have something like this?